000 AXNT20 KNHC 300555 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SAT APR 30 2011 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTION OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...ITCZ... ITCZ AXIS IS FROM 07N11W TO THE EQUATOR NEAR 24W...THEN ALONG THE EQUATOR TO 36W. ISOLATED MODERATE TO STRONG CONVECTION IS FROM 02N-06N BETWEEN THE PRIME MERIDIAN TO 07W. ISOLATED MODERATE TO STRONG CONVECTION IS FROM 01N-05N BETWEEN 11W-15W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL SHORTWAVE TROUGH IS ACROSS THE NE GULF AND IS PART OF A BROADER SCALE UPPER LEVEL TROUGH WITH AXIS EXTENDING ALONG THE EASTERN U.S. SEABOARD FROM THE NEW ENGLAND STATES TO NEAR 30N80W THEN INTO THE NE GULF WITH A BASE NEAR 27N84W. THIS UPPER LEVEL FEATURE SUPPORTS A COLD FRONT THAT EXTENDS ACROSS THE W ATLC AND SOUTHERN TIP OF THE FLORIDA PENINSULA AND CONTINUES AS A DISSIPATING COLD FRONT INTO THE SE GULF FROM 25N81W TO 24N90W. MOST ACTIVE CONVECTION REMAINS ACROSS THE W ATLC AND NW BAHAMAS THIS EVENING AS MOSTLY DRY AND SUBSIDENT W-NW FLOW DOMINATES ACROSS THE GULF AS NOTED ON WATER VAPOR IMAGERY. A WEAK SURFACE RIDGE IS OVER THE NE GULF ANCHORED BY A 1017 MB HIGH CENTERED OVER THE FLORIDA PANHANDLE NEAR 30N85W. RETURN S-SE FLOW IN THE RANGE OF 10 TO 20 KT...HIGHEST OVER THE NW GULF...IS LOCATED ON THE WESTERN PERIPHERY OF THE RIDGE AND IS EXPECTED TO PERSIST THROUGH EARLY TUESDAY. ON TUESDAY...A COLD FRONT WILL EMERGE OFF THE TEXAS AND LOUISIANA GULF COASTS AND QUICKLY SWEEP EASTWARD INTO THE W ATLC BY EARLY WEDNESDAY. CARIBBEAN SEA... MOSTLY WESTERLY UPPER LEVEL FLOW DOMINATES ACROSS MUCH OF THE CARIBBEAN AND WATER VAPOR IMAGERY INDICATES MODERATELY DRY AIR AND SUBSIDENCE IS PROVIDING FOR OVERALL STABLE ATMOSPHERIC CONDITIONS THIS EVENING. A WEAK UPPER LEVEL SHORTWAVE TROUGH IS HOWEVER LOCATED OVER THE NE CARIBBEAN AND IS HELPING TO ENHANCE WIDELY SCATTERED LOW-TOPPED OVER THE BASIN EAST OF 69W. THIS AREA COINCIDES WITH STRONGER EASTERLY TRADES AS DEPICTED ON EARLIER EVENING WINDSAT AND ASCAT SCATTEROMETER PASSES. WINDS TO 20 KT WERE NOTED IN THOSE PASSES E OF 74W. ANOTHER AREA OF ISOLATED SHOWER ACTIVITY IS LOCATED WITHIN 90 NM S OF THE COAST OF CUBA BETWEEN 79W-82W. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH AXIS EXTENDS FROM THE NEW ENGLAND STATES S-SW ALONG THE EASTERN U.S. SEABOARD AND SUPPORTS A COLD FRONT EXTENDING INTO THE SW NORTH ATLC NEAR 32N74W. THE FRONT CONTINUES SW TO THE FAR SOUTHERN FLORIDA PENINSULA NEAR BISCAYNE BAY AND INTO THE SE GULF OF MEXICO. LOW-LEVEL CONVERGENCE EAST OF AND ALONG THE FRONT IS GENERATING WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 120 NM EITHER SIDE OF THE FRONT AND IN THE VICINITY OF THE NW BAHAMAS FROM 25N-28N BETWEEN 75W-80W. THE FRONT IS FORECAST TO SHIFT NE OF 30N70W BY LATE SATURDAY INTO EARLY SUNDAY WITH LIGHT EASTERLY FLOW ONCE AGAIN ESTABLISHING ITSELF OVER THE SW NORTH ATLC W OF 70W. THE REMAINDER OF THE CENTRAL AND EASTERN ATLC THIS EVENING IS UNDER THE INFLUENCE OF A VERY BROAD SURFACE RIDGE ANCHORED BY A 1028 MB HIGH CENTERED NEAR 34N50W. A WEAK COLD FRONT EXTENDS ALONG 32N BETWEEN 22W-35W AND CONTINUES TO WEAKEN AS IT APPROACHES 30N. THIS FRONT IS SUPPORTED BY AN UPPER LEVEL LOW CENTERED OFF THE IBERIAN PENINSULA NEAR 38N19W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN